Former Pennsylvania governor and GOP congressman Tom Ridge has announced he will not be voting for Donald Trump in November’s general election.

Writing for U.S. News & World Report on Tuesday, Ridge said that Trump was a bully whose “bombastic tone” did not reflect the traits of a true politician.

He also went on to add that Trump’s “bumper sticker approach to policy” had failed to unite Republicans, and he placed doubt on whether the presumptive GOP nominee would be able to win over the American people in November.

As a result, Ridge said that he “simply cannot” endorse Trump for president.

“Every four years since my 18th birthday, I have pulled the lever in support of the Republican nominee for President of the United States,” he wrote on Tuesday. “That streak will end this November.”

A close ally of George W. Bush, Ridge has been a prominent Republican figure since the 1980s, when he was elected to represent Pennsylvania in the U.S. House of Representatives.

Ridge spent six terms in Congress before he was elected Pennsylvania’s governor in 1995. He also served as the nation’s first-ever Secretary of Homeland Security.

Yet despite that impressive GOP resume, Ridge said his disregard for Trump is simply too great in order to vote along party lines in this year’s election.

“Suffice to say that I am disappointed that he is our party’s nominee,” Ridge said. “With a bumper sticker approach to policy, his bombastic tone reflects the traits of a bully, not an American president and statesman. If he cannot unite Republicans, how can he unite America? I simply cannot endorse him.”

“I think Donald Trump is about celebrities, he’s about publicity, he’s not about bringing a serious mindset toward trying to address the wide range of security challenges in this country,” Ridge told Jeb Bush supporters at a rally in New Hampshire. “I just think he’s an embarrassment to the party, he’s an embarrassment to my country.”

Ridge is only the latest in a string of prominent Republican politicians to turn their backs on the party’s inevitable presidential nominee. Senator Lindsay Graham, Massachusetts Governor Charlie Baker, and the entire Bush clan have all said they will not be voting for Trump.

According to one poll conducted last month by Suffolk University, nearly one in five GOP supporters are planning to vote for Hillary Clinton if she ends up facing off against Trump in November.

Yet Tom Ridge was quick to point out Tuesday that he would not be among them.

“I cannot support Hillary Clinton, a divisive and untrustworthy candidate who will advance and extend failed Obama policies that have greatly weakened our nation’s economy and security,” he wrote.

That said, Ridge did say that he would ultimately support America’s decision in November – and he added he would do everything within his power to ensure the nation’s next president finds success in office.

“While I cannot endorse either candidate, whoever wins will be my president, too. And so I will help to advance their success in any way that I can,” he said. “Because while I began to learn what it means to be a Republican carrying that heavy bag so many years ago, my years in public service have only served to affirm that duty and loyalty to our nation must always come first.”